Forced flow steam generator having plural tube systems



April 26, 1966 H. VOGLER 3,247,830

FORCED FLOW STEAM GENERATOR HAVING PLURAL TUBE SYSTEMS Filed May 24, 1963 5 Sheets-Sheet 1 Jnvenfor: Hans, Vogler 63W Z 1:! Z

ATTORNEYS April 26, 1966 H. VOGLER FORCED FLOW STEAM GENERATOR HAVING PLURAL TUBE SYSTEMS Filed May 24, 1963 5 Sheets-Sheet 2.

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a A Q Jnvenfor: Hons Vogler 611W; I EGLVMMLM ATTORNEYS H. VOGLER April 26, 1966 FORCED FLOW STEAM GENERATOR HAVING PLURAL TUBE SYSTEMS 5 Sheets-Sheet 3 Filed May 24, 1963 Jnvenfor: Finns Vogler G) is? h m-41 ML QM ATTORNEYS H. VOGLER A ril 26, 1966 FORCED FLOW STEAM GENERATOR HAVING PLURAL TUBE SYSTEMS 5 Sheets-Sheet 4 Filed May 24, 1965 Jnvemor: Hons Vogler M CLOLMLJ ATTORNEYS 115 x I i? l 2 Q 7 x M w a 3 RH E 0 April 26, 1966 H. VOGLER 3,247,830

FORCED FLOW STEAM GENERATOR HAVING PLURAL TUBE SYSTEMS Filed May 24, 1963 5 Sheets-Sheet 5 INVENTOR Hons Vogler BY W ATTORNEYS United States Patent Ofi ice Patented Apr. 26, 1966 3,247,830 FORCED FLOW STEAM GENERATQR HAVING PLURAL TUBE SYTEMS Hans Vogler, Winterthur, Switzerland, assignor to Sulzer Brothers Limited, Winterthur, Switzerland, 2 Swiss company Filed May 24, 1963, Ser. No. M2310 Claims priority, application Switzerland, .lune 8, 1962, 6,922/ 62 8 tllaims. (Cl. 122-235) This invention relates to forced flow steam generators having plural tube systems. In high capacity steam generators of this type, the parallel tube sets are customarily divided into two or more separate tube systems of which each includes at least two heat exchange surfaces traversed in series by the working substance, each heat exchange surface in turn including a plurality of parallel-connected tubes through which the working substance flows. In such an arrangement the tube systems are traversed by unlike quantities of working substance, corresponding to their individual heat absorption capacities, the amount of heat falling upon these surfaces in the firing chamber being unlike in view of the asymmetry in the position of the fire. By means of such a separation into parallel channels, there is achieved a uniform heating of the working substance and of the various parallel connected tube sets.

If plural heat sources are provided in the steam generator, the tube systems are allocated to the individual heat sources. In the case however of a single fire or heat source, it has been customary heretofore to arrange the tube sets in closed form. That is to say, in boilers having a double U firing arrangement, the walls of the firing chamber on the side of one row of burners are lined with tubes of one tube system whereas the walls on the side of the other row of burners are lined with tubes from the other tube system. In this way, it is sought to achieve as uniform a firing as possible of the channels in the individual tube systems.

With certain fuels the position of the flame tends to instability, particularly in double U-shaped firing arrangements, so that the steaming tubes are exposed to nonuniform heating. That is, although the quantity of working substance passed through the individual tube systems is approximately proportioned to their individual heat absorption capacities by the subdivision and distribution of tubes, nonetheless those parts of the individual tube systems in which the individual heat absorption is most uniform, as for example the economizer and preheater elements which are heated by flue gases, are subjected to non-uniform cooling by the working substance flowing therethrough. In consequence, there may occur hot spots in such systems which require the injection of excessive amounts of cooling water.

It has therefore already been proposed to protect against such localized overheating those parts of the tube system which follow the evaporator (the evaporator itself being usually disposed for the most part in the firing chamber itself) by equalizing at least once the initially unequal quantities of working substance in the separate tube systems. In the evaporator itself however this method does not correct an unequal loading of the various tube systems.

According to the invention, there is corrected in the evaporator itself a variable heating of the working sub stance, particularly such as may occur upon temporary and accidental displacements of the flame pattern. This result is achieved by dividing each tube system, at least as to the part thereof which serves to cool the firing chamher, into two separate series-connected sections which are so disposed on the firebox walls that for every accidental displacement of the flame pattern to a position which is asymmetric with respect to the boiler axis, the changes in heat exposure of these two sections occur in opposite senses.

For this purpose the two sections of a tube system may be disposed symmetrically to the vertical central axis of the firing chamber. Alternatively in the case of double U-shaped firing arrangements, they may be disposed symmetrically with respect to the median plane of the firing chamber, which median plane extends parallel to the rows of burners. If the firing chamber possesses unlike dimensions in the directions of its two principal axes, then the sections of each tube system are advantageously distributed along these two dimensions.

It is further advantageous in an arrangement according to the invention to dispose the sections of each tube system at various heights within the firing chamber. It is also possible to join the individual sections of a tube system directly without the provision of collectors or headers between them. It is also advantageous so to dispose the elements of the system that the fiow of working substance occurs in the individual sections of two tube systems in such fashion that the working substance in directly adjacent tubes of two systems will possess at least approximately the same temperature. Lastly, two sections of a tube system may be joined together by means of a heat exchange surface in another portion of the boiler, for example the funnel-shaped portion at the bottom of the firing chamber.

The invention will now be further described with reference to the accompanying drawings in which:

FIG. 1 is a vertical sectional view through a forced flow boiler having a double U firing arrangement;

FIG. 2 is a plan sectional view taken on the line IIII of FIG. 1; and

FIGS. 3 to 11 are diagrammatic representations of various arrangements for the sections of the invidiual tube systems of the steam generator of FIGS. 1 and 2. FIGS. 2, 5 and 7 show two tube systems whereas FIGS. 6, 8 and 9 represent steam generators according to the invention having four tube systems distributed over the firebox walls. FIGS. 1 to 7 presuppose a double U-shaped firing whereas FIGS. 8 and 9 pertain to corner-fired chambers. FIG. 10 is a diagrammatic representation in plan of another arrangement for the sections of the tubesystems in a steam generator according to the invention in which two series-connected sections in each tube system are disposed serially along the vertical dimension of a firing chamber, as well as along the horizontal. FIG. 11 is a diagrammatic representation of still another arother arrangement of the sections of the tube systems of a steam generator in accordance with the invention wherein each tube system includes two sections disposed in the firing chamber symmetrically with respect to an equilibrium position for a firing means and a further section in series with the first two but along the funnelshaped walls 4a and 4b which serve for the collection of ashes and which are beneath the equilibrium position of the flames produced by the burners, as indicated in FIG. 1.

The steam generator of FIG. 1 comprises a portion or zone heated primarily by radiation, a horizontal duct 2, and a vertical duct 3 in which the heating takes place by means of the products of combustion. The radiation zone comprises lower and upper portions 1a and 1b of the firing chamber. To the lower end of portion 1a are connected the funnel shaped portions 4a and 412 for collection of ashes. The upper portion of this radiation zone is denoted 1b. The portion 1b possesses a smaller crosssection than the portion 1a. posed along each of the two narrow sides of the lower A set 5 of burners is disportion 1a as illustrated in FIGS. 1 and 2. Each set of burners comprises a row of burners 6. In consequence, as indicated schematically by the shape of the flames in FIG. 1, the steam generator is provided with so-called double U firing. 1

The steam tubing 7 of the firing chamber comprises, in the lower portion 1a of the firing chamber, two separate sinuous tube systems A and B. As shown in FIG. 2, the system A possesses an input header 10A and two walllining tube screen sectors 21 and 22, at the downstream end of which the tubes 7 thereof terminate in a header 11A. The sectors 21 and 22 substantially cover at least the lower vertical walls of the firing chamber, over substantially one-half of the short and long dimensions respectively of the firing chamber as seen in section in FIG. 2.

The header 11A in turn connects with header 12A via a line 29. From header 12A the tubes 7' of the A system return to the firing chamber and cover the sectors 25 and 26 of the firing chamber walls before opening into the outlet header 13A.

correspondingly the tube system B comprises the headers and distributors 10B, 11B, 12B and 13B, together with tubing which covers the wall sectors 28, 27, 24 and 23, the headers 11B and 12B being connected together by the conduit outside the firing chamber.

Of course, the upper portion 1b of the firing chamber may be provided with two tube systems in the same or in a similar fashion.

In the embodiment according to FIG. 2, there is provided between the first section of one tube system, comprising sectors 21, 22, and the second section comprising sectors 25, 26, a collector 11A and a distributor 12A, and similarly there is provided in the second tube system between the first section comprising sectors 27, 28 and the second section comprising sectors 23, 24, a collector 11B and a distributor 128. In many cases it is possible to lead the tube sets without interruption from the first to the second section. Alternatively, other heat exchange surfaces may be provided between the first and second sections of each system. These supplementary heat exchange surfaces may for example serve to cool the funnel-shaped walls 4a and 4b of the firing chamber.

If now the flame pattern shifts as a wholeassuming for the sake of simplicity a shift in the center of gravity of the totality of flames-and if for example the shift takes place to the right in the views of FIGS. 1 and 2, then the firing of the sections 25, 26 of tube system A and of sections 23, 24 of tube system B will be increased whereas that of the sections 21, 22 of system A and of sections 27, 28 of system B will be reduced. In contrast to the usual arrangements ofthe prior art in which, for example, the system A was disposed wholly in the lefthand portion and system B wholly in the righthand portion of the lower firing chamber 111, so that upon shift in the flame pattern there occurred a substantial change in the exposure to the fire of the tube systems, in accordance with the invention the variation in heat exposure is substantially balanced out by the variable heating of the separate sections of each system. Consequently, the quantities of working substance which flow through the separate tube systems may be made substantially equal although, as previously indicated, these quantities are proportioned to the individual heat absorption capacities of the various tube systems. In this way there is achieved the result that the superheater and economizer sections as well as the tube sections of the evaporator are substantially equally cooled by the working substance flowing therethrough.

FIG. 3 shows an arrangement of two tube systems A and B similar to that of FIG. 2 but in still further schematic form for the sake of clarity. In this embodiment, in contrast to FIG. 2, the inlet headers are disposed along the long side of the firing chamber walls.

In FIG. 3 the sections of the tube system A are identified by reference characters 31, 32, and 36, these correspondingly generally to the reference characters of same lowest ordinal digit 21, 22, 25 and 26 in FIG. 2. The sections 31, 32, 35 and 36 of FIG. 3 are connected together by means of the conduit 39 The system B of FIG. 3 comprises an analogous fashion the fire box wall tube sections 38, 37, 34 and 33, connected together by means of the conduit 40.

The embodiment of FIG. 4 ditfers from that of FIG. 3 simply in that the direction of flow of working substance in the sections 46 and of system A and in sectors 43 and 44 of the system B is reversed, flow proceeding from section 46 to 45 and from section 43 to 44 whereas in FIG. 3 the direction of flow was from 35 to 36 and from 34 to 33. The arrangement of FIG. 4 possesses therefore the additional advantage that the continguous sections 42 and 43 on the one hand and 46 and 47 on the other hand of the two systems A and B are arranged so that at their points of nearest approach to each other they possess tubes of approximately the same temperature for the working substance therein. This is desirable for the sake of uniform thermal expansion, particularly in boilers without masonry walls.

The embodiments of FIGS. 2 to 4 possess symmetry with respect to the vertical central axis of the firing chamber 1.

In the embodiment according to FIG. 5, the tubing of the firing chamber walls is divided into six sections. Of these the sections 53, and 51 belong to tube system A and the sections 56, 52 and 54 belong to system B. The tube sections of system A are connected in series by means of conduits 57 and 59 whereas the sections of system B are connected in series by conduits 60 and 58. In this embodiment there exists symmetry of the individual sections of the two tube systems with respect to the median plane of the chamber 1a, this being a plane parallel to the rows of burners.

The symmetry here in question concerns only the interconnection and disposition of the individual sections of the tube systems and not the number or length of the individual tubes 7. Thus in FIG. 5 the upstream sections 53 and 56 of systems A and B respectively comprise a smaller number of tubes 7 than the downstream sections 51 and 54. Within system therefore the number of tubes 7 is increased in known fashion, fo rexample, by branching arrangements, in order to compensate for increase in the specific volume of the working substance consequent upon its rise in temperature. In this way also the decline in temperature difference At between the heat source and the working substance at high temperature on a downstream heat exchange surface may be compensated, particularly in parts of the firing chamber such as the part 1b (FIG. 1) in which heat transfer does not occur exclusively by radiation, such compensation being elfected by increase in the surface of such a downstream section. Such a change or alteration in the heating surface for the working substance within any one system is of course also applicable with suitable modification to the other embodiments of the invention.

FIG. 6 shows an embodiment in which the tube sets are divided into four systems. The arrangement of the systems and their individual sections is as follows: System A comprises at its upstream end a section 62, then a junction conduit 69A and section 65. System B comprises section 63, conduit 69B and section 68, while section 66, conduit 69C and section 61 make up section C. The system D comprises sections 67 and 64 connected in series by conduit 69D. In the embodiment of FIG. 6 the systems are so disposed over the firing chamber that each system includes at least one section extending in the direction of a principal axis parallel to the rows of burners whereas the second section extends perpendicularly to that direction.

The embodiment of FIG. 7 possesses again two systems A and B divided into ten sections, possessing the same symmetry as the example of FIG. 5. Specifically, system A comprises the sections 70, 72, 74, 76 and 78 which are connected together in series by the conduits 80, 82, 84 and 86 outside the firing chamber. In similar fashion sections 79, 77, 75, 73 and 71 and conduits 87, 35, 33 and 81 make up system B.

Whereas all embodiments of the invention thus far described include double U firing, FIGS. 8 and 9 illustrate two steam generators according to the invention employing corner burners 90 at all four corners of the firing chamber. In both of these embodiments the tubes within the firing chamber are divided into four tube systems A to D. In FIG. 8 this tubing is made up of twelve sections.

More particularly, referring to FIG. 8, the system A includes sections 91, 97 and 99 with junction conduits 103 and 104, whereas system B comprises sections 98, 92 and 102, connected together by means of conduits 105 and 1%. In the system C the working substance passes into the section 100 and passes via a conduit 107 into section 94 before it flows through the conduit 108 and the section 96 to leave the system C. System D comprises sections 101, 95 and 93 and junction conduits 109 and 110. Although a general symmetry is not present in this embodiment, even here the individual sections of the separate systems are so disposed that upon a random displacement of the flame pattern, at least as to two series-connected sections of each tube system, there occurs a variation in opposite senses of the firing thereof.

In contrast FIG. 9 shows again an arrangement symmetrical with respect to the vertical central axis of the firing chamber. The system A here comprises sectors 112 and 116 and the conduit 119. System B comprises sections 113 and 117 and conduit 120. Sections 114 and section 118 together with conduit 121 make up the system C whereas system D comprises sections 115 and 111 and the conduit 122.

In FIG. 10, as in FIG; 3 for example, two tube systems A and B are seen in plan. In the system A the working substance flows through a section 130 disposed in the lower part of the firing chamber (the part 1a in FIG. 1). The working substance flows thence through a connecting line 131 into a section 132 disposed at another level, as for example in the upper part 1b in the firing chamber of FIG. 1. From the section 132 the working substance flows through another conduit 133 to a third section 134 disposed in the lower part of the firing chamber and thence through a conduit 135 to a fourth section 136 disposed in the upper part of the firing chamber. In similar fashion the tube system B comprises four sections 138, 140, 142 and 144 connected in series by junction conduits 139, 141 and 143, with the sections 138 and 142 in the lower part of the firing chamber and with the sections 140 and 144 in the upper part of the firing chamber.

In FIG. 11 there is shown in highly schematic form an embodiment of the invention in which there are disposed between the firing chamber tube sections of each of the systems A and B heat transfer surfaces elsewhere disposed in the boiler, namely in the hopper indicated at 4a or 4b in FIG. 1. In this example the tube system A includes the firing chamber tube sections 150 and 152 and an intermediate heat transfer surface 154, all connected in series by conduits 151 and 153. The heat transfer surface 154 is arranged on the inclined sloping walls of the hopper, and the tubes in this transfer surface 154 extend horizontally over one of the long and one of the short oblique walls of the hopper. The tube system B includes in similar sections 155 and 156 disposed over parts of the firing chamber walls, and a supplementary heat transfer surface in the form of a set of tubes 157 spread over one of the long and one of the short lower oblique sloping sides of the hopper, at the left in FIG. 11. The system B thus includes tube sections 155 and 156 on the walls of the firing chamber and the heat transfer surface 157 in the hop- 6 per. Conduits 158 and 159 serve to connect together in series the individual sections 155, 156 and 157 of the tube system B.

Of course the invention is not limited to the particular constructions which have been shown and described, various other arrangements being possible in which for example the number of sections and the number of tube systems may be appropriately varied. Moreover, it is possible within the scope of the invention to dispose the individual sections not only around the periphery of the firing chamber but also along the vertical dimension of the firing chamber within the portions 1a and 1b thereof individually and also over the height of the firing chamber taken as a whole. The invention is also applicable to both forced circulation steam generators, in which the flow is forced but in which the working substance may pass repeatedly over the same heat exchange surfaces, and also to once-through forced flow steam generators, in which the working substance flows over any one heat exchange surface only once in a single pass through the steam generator. The scope of the invention is thus not limited to the embodiments illustrated and described,

being rather set out in the accompanying claims.

I claim:

1. A forced flow steam generator comprising a heat source and a plurality of tube systems surrounding and exposed to said source, each tube system including at least two series-connected sections so disposed on opposite sides of said source at substantially equal heights with the two sections of each system spaced from each other circumferentially of said source by at least one section of another of said systems that upon displacement of said source in any of plural non-parallel directions from an equilibrium position the exposure of one of said two sections to said source is increased while the exposure of the other of said two sections to said source is decreased.

2. A forced flow steam generator comprising a firing chamber, means to generate a flame at an equilibrium position in said chamber, and a plurality of tube systems disposed in said chamber around said position, each tube system including at least two series-connected sections so disposed at substantially equal heights on opposite sides of said equilibrium position with said two sections of each system spaced from each other circumferentially of said position by at least one section of another of said systems that variations in position of said flame along any of plural non-parallel directions subject one of said two sections to more intense and the other of said two sections to less intense firing from said flame.

3. A forced flow steam generator comprising a firing chamber having a central vertical axis, and a plurality of tube systems in said chamber, each tube system including at least two series-connected sections, the two sections of each of said systems being substantially symmetrically disposed with respect to said axis at substantially equal heights and spaced from each other circumferentially of said axis by at least one section of another of said tube systems.

4. A forced flow steam generator comprising a firing chamber, means to generate in said chamber a flame having an equilibrium position, a plurality of tube systems in said firing chamber, each of said tube systems including at least two sections symmetrically disposed with respect to said equilibrium position at substantially equal heights and spaced from each other circumferentially of said position by at least one section of another of said systems, and separate means to connect in series the two said sections of each system with the inlet to the downstream section of one system adjacent the outlet to the upstream section of another of said systems.

5. A forced flow steam generator comprising a firing chamber having four mutually transverse walls, means to generate in said chamber a flame having an equilibrium position, and a plurality of tube systems in said chamber, each tube system including at least four series-connected sections with the said sections of all of said systems disposed at substantially the same height and with one secones of said walls and said two pairs being symmetrically disposed with respect to said equilibrium position and spaced from each other circumferentially of said position by one pair of sections from another of said systems.

6. A forced circulation steam generator comprising a firing chamber, means to generate in said chamber a flame having an equilibrium position, and a plurality of tube systems, at least one tube systems each including at least two series-connected tube sections disposed in said chamber at substantially the same height on opposite sides of said position and spaced from each other circumferentially of said position by a section of another of said systems, each of said systems further including a further tube section connected in series with and between said two sections, said further tube section being disposed below said equilibrium position.

7. A forced flow steam generator comprising a heat source having an equilibrium position and a plurality of tube systems exposed to said source, each tube system including at least two series-connected sections at substantially the same height with respect to said position, the said two sections of each system being spaced from each other circumferentially of said position by at least one section of another of said systems.

8. A forced flow steam generator comprising a heat source having an equilibrium position from which it is susceptible of displacement and a plurality of tube systems exposed to said source, each tube system including at least two series-connected sections at substantially the same height with respect to said position, the two said sections of each system being disposed on opposite sides of said position and being separated from each other peripherally of said position by at least one section of another of said systems.

References Cited by the Examiner UNITED STATES PATENTS 2,896,591 7/1959 Schoedter 122235 2,905,155 9/1959 Grossman 122478 2,989,036 6/1961 Hake et a1 122235 2,999,483 9/ 1961 Armacost 1225 10 3,081,748 3/1963 Koch 122-406 3,105,466 10/1963 Evans 122235 FOREIGN PATENTS 870,735 6/1961 Great Britain.

FREDERICK L. MATTESON, IR., Primary Examiner.

MEYER PERLIN, ROBERT A. OLEARY, Examiners. 

1. FORCED FLOW STEAM GENERATOR COMPRISING A HEAT SOURCE AND A PLURALITY OF THE SYSTEM SURROUNDING AND EXPOSED TO SAID SOURCE, EACH TUBE SYSTEM INCLUDING AT LEAST TWO SERIES-CONNECTED SECTIONS SO DISPOSED ON OPPOSITE SIDES OF SAID SOURCE AT SUBSTANTIALLY EQUAL HEIGHTS WITH THE TWO SECTIONS OF EACH SYSTEM SPACED FROM EACH OTHER CIRCUMFERENTIALLY OF SAID SOURCE BY AT LEAST ONE SECTION OF ANOTHER OF SAID SYSTEMS THAT UPON DISPLACEMENT OF SAID SOURCE IN ANY OF PLURAL NON-PARALLEL DIRECTIONS FROM AN EQUILIBRIUM POSITION THE EXPOSURE OF ONE OF SAID TWO SECTIONS TO SAID SOURCE IS INCREASED WHILE THE EXPOSURE OF THE OTHER OF SAID TWO SECTIONS TO SAID SOURCE IS DECREASED. 